1. Field of the Invention
The field of the invention relates to transmissions. More particularly the invention relates to continuously variable transmissions.
2. Description of the Related Art
In order to provide an infinitely variable transmission, various traction roller transmissions in which power is transmitted through traction rollers supported in a housing between torque input and output disks have been developed. In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause the engagement of traction rollers with the torque disks in circles of varying diameters depending on the desired transmission ratio.
However, the success of these traditional solutions have been limited. For example, in U.S. Pat. No. 5,236,403 to Schievelbusch, a driving hub for a vehicle with a variable adjustable transmission ratio is disclosed. Schievelbusch teaches the use of two iris plates, one on each side of the traction rollers, to tilt the axis of rotation of each of the rollers. However, the use of iris plates can be very complicated due to the large number of parts which are required to adjust the iris plates during shifting the transmission. Another difficulty with this transmission is that it has a guide ring which is configured to be predominantly stationary in relation to each of the rollers. Since the guide ring is stationary, shifting the axis of rotation of each of the traction rollers is difficult. Yet another limitation of this design is that it requires the use of two half axles, one on each side of the rollers, to provide a gap in the middle of the two half axles. The gap is necessary because the rollers are shifted with rotating motion instead of sliding linear motion. The use of two axles is not desirable and requires a complex fastening system to prevent the axles from bending when the transmission is accidentally bumped, is as often the case when a transmission is employed in a vehicle. Yet another limitation of this design is that it does not provide for an automatic transmission.
Therefore, there is a need for a continuously variable transmission with a simpler shifting method, a single axle, and a support ring having a substantially uniform outer surface. Additionally, there is a need for an automatic traction roller transmission which is configured to shift automatically. Further, the practical commercialization of traction roller transmissions requires improvements in the reliability, ease of shifting, function and simplicity of the transmission.
The present invention includes a transmission, comprising three or more spherical power adjusters, each power adjuster having a cylindrical hole extending through its center and three or more cylindrical spindles with each spindle positioned in the hole of one power adjuster. There may be at least one stationary support with an aperture at its center and a rotatable support member having first and second sides. The rotatable support member can be located between the power adjusters and frictionally engaged with the plurality of power adjusters. The rotatable support member can have a substantially uniform outer diameter, and is capable of axial movement. The rotatable support member may have at least two areas that are bearing surfaces to control axial movement of the rotatable support member. Interacting with the rotatable support member is a first annular bearing, capable of axial movement, is positioned on the first side of the support member and a second annular bearing capable of axial movement, positioned on the second side of the support member. A first planar platform capable of axial movement, is positioned so that the first annular bearing is between the rotatable support member and the first planar platform. A second planar platform, capable of axial movement, is positioned so that the second annular bearing is between the rotatable support and the second planar platform. A ratio changer operably connected to the cylindrical spindles causes the cylindrical spindles to change their axes of rotation.
One embodiment includes a transmission, comprising a drive sleeve with three or more ramped surfaces on the drive sleeve that face the rotatable driving member. Three or more rollers are positioned to roll on the three or more ramped surfaces of the drive sleeve and also roll on the rotatable driving member. A roller cage positions the three or more rollers. The three or more ramped surfaces of the drive sleeve are configured so that when the three or more rollers rotate they compress the rotatable driving member against the three or more spherical power adjusters upon an increase in torque and decompress the rotatable driving member upon a decrease in torque. The embodiment may have at least one stationary support with an aperture at its center.
Yet another embodiment includes a plurality of legs rigidly attached to the at least one stationary support. The plurality of legs extend in a direction from the at least one stationary support towards the spherical power adjusters. The plurality of legs are designed to assist in holding the spherical power adjusters in a stationary position.
Another embodiment includes a shifting member having an end that extends outside of the transmission. The shifting member is positioned along the axis of the rotatable support member and is operably engaged with the rotatable support member. An adjustment in the position of the shifting member causes the rotatable support member, the first annular bearing, the second annular bearing, the first planar platform, and the second planar platform to all move simultaneously and a substantially equal distance.